22 December 2013

Going Grinch on Time

I should be happy that Marmorkrebs is getting attention in national media, namely Time magazine. Instead, my reaction is more like:

The annoyance starts with the title:

“Critters So Ugly They Have to Mate With Themselves”

It’s not the critters that are ugly, it’s the title. Time used to have a little more dignity, but this sounds like it came from Buzzfeed. How demeaning to call these animals “ugly,” especially when the list contains not just the pretty marbled crayfish, but the handsome Komodo dragon (which doesn’t always reproduce asexually, putting like to the “have to” portion of the title), the sleek whiptail lizard, and the amazing looking hammerhead shark (which, again, doesn’t always reproduce asexually). “Mate with themselves” suggests self-fertilization, which some animals do, but these are all cases of parthenogenesis rather than self-fertilization

The subtitle isn’t better.

Immaculate conception may be something special among humans, but in the animal kingdom, it's always been part of the mix

Science and religion are often depicted as being at war, but they are united in the desire for good fact checking. The immaculate conception is not about the virgin birth of Jesus Christ. It’s about the conception of the Jesus’s mother, Mary, free of original sin.

I’m reminded of this anecdote from Christopher Hitchens:

I made a mistake with one guy on a radio station in Seattle. I said I don’t think anyone really believes in the virgin birth and he said ‘I do.’ I said ‘you don’t really’ and he said, ‘I do, I believe absolutely in the immaculate conception.’ I told him he’d got it wrong and he said ‘What do you mean I’ve got it wrong? I’ve been a Catholic all my life.’ The immaculate conception and the virgin birth are two different concepts. He didn’t get this, but he believed in both.

The article manages to squeeze in three alternate spellings for Marmorkrebs in an equal number of paragraphs: “marmorkrebs,” and “Marmokrebs” (sic), both in a capitalized version (preferred here on the blog, following the German practice of capitalizing all nouns) and not.

And to add insult, the article is illustrated with this:

It’s not even a picture of the right species! It’s Procambarus clarkii, the common Louisiana red swamp crayfish! There are no shortage of Marmorkrebs pictures for use on this website and elsewhere. Time, you could have emailed me.

On the plus side, article does a nice job of linking to full text of the original scientific articles. And the actual text of the article, though short, is otherwise accurate.

External links

Critters So Ugly They Have to Mate With Themselves

18 December 2013

Human parthenogenesis, according to pregnant women

Christmas is the best time of the year to tell people about parthenogenesis, seeing that a story of human parthenogenesis forms a large part of Christmas tradition.

The British Medical Journal (or BMJ) has a new paper out that looks closely at reports of parthenogenesis in humans. According to Herring and colleagues, of over 7,000 young women (about 12-18) surveyed, about 0.8% of women reported pregnancy before they reported having sex.

As far as I can tell, they did not ask the women outright if they believed they got pregnant without the help of a man. They just extrapolated from whether women reported having had sex, whether they reported being pregnant, and comparing the dates. However, it seems likely that the women might have claimed virgin birth, given this interesting fact:

The virgins who reported pregnancies were more likely to have pledged chastity (30.5%) than the non-virgins who reported pregnancies (15.0%, P=0.01) or the other virgins (21.2%, P=0.007).

Also of note:

The virgins who reported pregnancy... were less likely to know how to use condoms than the non-virgins who reported pregnancy (79.6%, P=0.002).

The discussion mentions another fascinating group: the “born again virgins,” who reported having had sex early in the study, but reported themselves as virgins when surveyed again. This is actually much more common than virgin birth, accounting for about 3% of the women surveyed. This might be almost as miraculous as virgin birth.

I think there may be a few issues with self-reporting in this data set.

In addition to the interesting data, this paper also gets high points from me for referencing a Doctor Who episode in the introduction.


Herring AH, Attard SM, Gordon-Larsen P, Joyner WH, Halpern CT. 2013. Like a virgin (mother): analysis of data from a longitudinal, US population representative sample survey. BMJ 347 http://dx.doi.org/10.1136/bmj.f7102

Related post

Human parthenogenesis?

External links

Claims of virgin births in U.S. near 1 percent: study
Christmas Miracle? One In 200 US Pregnancies Reportedly Involve Virgin Mothers

Top image from here.

11 December 2013

New name, new problems

The scientific name for Marmorkrebs continues to pose problems. First, the problem was that it didn’t have one. Then, Martin and colleagues (2010) proposed Procambarus fallax f. virginalis. The good news is that this name has been adopted by the scientific community. The bad news is that people are shortening it.

Because I am interested in the biology of both the sexual slough crayfish and the asexual Marmorkrebs, I have Google Scholar alerts set up for both. Recently, Google Scholar sent me a new “Procambarus fallax” alert for a new paper in Ecology and Evolution. The species appear in Table 1 and in the supplemental material.

I saw that the crayfish in the paper were bought in a pet store in the Netherlands, which made me wonder. The asexual Marmorkrebs are reportedly common in the European pet trade, but it was possible that this was the sexual form.

I emailed the authors, and co-author Menno Soes replied:

The examined specimen was the asexual form. In Dutch we call it marmerkreeft. I’ve never noticed the sexual form in Dutch pet shops.

Because this paper was about species living with crayfish, this distinction between slough crayfish and Marmorkrebs could change the interpretation slightly. If it was the sexual form, slough crayfish, it was conceivable that it was caught in the wild in Florida and shipped to Europe. If it was the asexual form, Marmorkrebs, this would be much less likely.

This isn’t the first time this has happened, either. Gallardo and Aldridge (2013) also used the species name Procambarus fallax alone, which significantly affects the interpretation of their results.

The moral of the story is: Authors and editors, please make sure to use the full species name for Marmorkrebs, Procambarus fallax f. virginalis, every time!


Gallardo B, Aldridge DC. 2013. The ‘dirty dozen’: socio-economic factors amplify the invasion potential of 12 high-risk aquatic invasive species in Great Britain and Ireland. Journal of Applied Ecology 50(3): 757–766. http://dx.doi.org/10.1111/1365-2664.12079

Martin P, Dorn NJ, Kawai T, van der Heiden C, Scholtz G. 2010. The enigmatic Marmorkrebs (marbled crayfish) is the parthenogenetic form of Procambarus fallax (Hagen, 1870). Contributions to Zoology 79(3): 107-118. http://dpc.uba.uva.nl/ctz/vol79/nr03/art03

Mestre A, Aguilar-Alberola JA, Baldry D, Balkis H, Ellis A, Gil-Delgado JA, Grabow K, Klobučar G, Kouba A, Maguire I, Martens A, Mülayim A, Rueda J, Scharf B, Soes M, S. Monrós J, Mesquita-Joanes F. 2013. Invasion biology in non-free-living species: interactions between abiotic (climatic) and biotic (host availability) factors in geographical space in crayfish commensals (Ostracoda, Entocytheridae). Ecology and Evolution: in press. http://dx.doi.org/10.1002/ece3.897

10 December 2013

Zieger and colleagues, 2013

Zieger E, Bräunig P, Harzsch S. 2013. A developmental study of serotonin-immunoreactive neurons in the embryonic brain of the marbled crayfish and the migratory locust: evidence for a homologous protocerebral group of neurons. Arthropod Structure & Development 42(6): 507-520. http://dx.doi.org/10.1016/j.asd.2013.08.004


It is well established that the brains of adult malacostracan crustaceans and winged insects display distinct homologies down to the level of single neuropils such as the central complex and the optic neuropils. We wanted to know if developing insect and crustacean brains also share similarities and therefore have explored how neurotransmitter systems arise during arthropod embryogenesis. Previously, Sintoni et al. (2007) had already reported a homology of an individually identified cluster of neurons in the embryonic crayfish and insect brain, the secondary head spot cells that express the Engrailed protein. In the present study, we have documented the ontogeny of the serotonergic system in embryonic brains of the Marbled Crayfish in comparison to Migratory Locust embryos using immunohistochemical methods combined with confocal laser-scan microscopy. In both species, we found a cluster of early emerging serotonin-immunoreactive neurons in the protocerebrum with neurites that cross to the contralateral brain hemisphere in a characteristic commissure suggesting a homology of this cell cluster. Our study is a first step towards a phylogenetic analysis of neurotransmitter system development and shows that, as for the ventral nerve cord, traits related to neurogenesis in the brain can provide valuable hints for resolving the much debated question of arthropod phylogeny.

Keywords: neurophylogeny • serotonin • neurotransmitter • neurogenesis • immunohistochemistry • crayfish • locust • embryo • brain • development

04 October 2013

Bohman and colleagues, 2013

Bohman P, Edsman L, Martin P, Scholtz G. 2013. The first Marmorkrebs (Decapoda: Astacida: Cambaridae) in Scandinavia. BioInvasions Records 2(3): 227–232. http://dx.doi.org/10.3391/bir.2013.2.3.09


Invasive crayfish have attracted much attention by scientists and policy makers in Europe, partly due to their ability to transmit diseases to native crayfish species. In December 2012, 13 specimens of a new crayfish species were found in the River Märstaån in central Sweden. Mitochondrial DNA analyses identified them as Marmorkrebs Procambarus fallax f. virginalis. It is not known if Marmorkrebs can establish reproducing populations in Sweden, and knowledge of how different stressors negatively affect the eventual reproduction of Marmorkrebs is lacking. Since the parthenogenetic Marmorkrebs has potential to become an invasive species in Sweden and Scandinavia, it may pose a serious threat to native crayfish, fish and fisheries. Swedish authorities have produced an action plan with a national strategy in order to establish a system that manages the import, movement and release of alien species and genotypes. The River Märstaån leads to Lake Mälaren, without barriers, which enhances the risk that the crayfish will also invade the lake. Due to the potential threat of further spread, it is imperative to make an action plan with a risk assessment targeted specifically towards the Marmorkrebs in River Märstaån.

Keywords: Procambarus fallax f. virginalis • parthenogenetic • crayfish • disease • risk analysis • action plan

17 September 2013

Plague poster

From Kärntner Institut für Seenforschung (roughly translated, the Carinthian Institute for Lake Research) comes this poster on whether Marmorkrebs can spread the dreaded crayfish plague (click to enlarge):

The short answer is yes, as predicted. Although they can carry it, there are still no reports of Marmorkrebs in the wild carrying crayfish plague that I know of.

This poster was presented at the 16th International Conference on Diseases of Fish and Shellfish. This meeting had a large symposium on crayfish plague.

External links

Kärntner Institut für Seenforschung
16th International Conference on Diseases of Fish and Shellfish

10 September 2013

Turning the tide

Marmorkrebs are a concern as an emerging invasive crayfish, but in much of the world, they still have a long way to go before they catch up with other exotic crayfish. In North American, a lot of attention has revolved around the rusty crayfish, Orconectes rusticus.

This article describes an effort to control rusty crayfish in a semi-natural setting that seemed to have worked. The abstract reports that they reduced the number of crayfish by 99% of where they started. The paper goes on to look at what happens to the lake when the crayfish are gone. As I’ve often said to people, “A lake with crayfish looks completely different than one without crayfish,” and this research bears that out.

How did the team get this invasive crayfish under control? Trapping, and a lot of elbow grease (my emphasis).

Hansen thinks that, if the right agency or lake association had the time and money to pay someone to extensively trap crayfish, it could work. But, she cautions, it’s a lot of work. Her group needed eight summers of full-time trapping to finally get rusty crayfish numbers where they wanted them.


Hansen GJA, Hein CL, Roth BM, Vander Zanden MJ, Gaeta JW, Latzka AW, Carpenter SR. 2013. Food web consequences of long-term invasive crayfish control. Canadian Journal of Fisheries and Aquatic Sciences 70:1109-1122. http://dx.doi.org/10.1139/cjfas-2012-0460

External links

In whole-lake experiment, have invasive crayfish met their match?

01 September 2013

Janský and Mutkovič, 2010

Janský V, Mutkovič A. 2010. Rak Procambarus sp. (Crustacea: Decapoda: Cambaridae) – prvý nález na slovensku. Acta Rerum Naturalium Musei Nationalis Slovaci 56: 64-67.


Marbled crayfish – Procambarus sp. (Crustacea: Decapoda: Cambaridae) – first find in Slovakia. The species was found in gravelpit near-by the village Koplotovce, in May 2010. Distribution of this species in Europe and its risk for our nature is discused (sic).

Keywords: marbled crayfish • distribution • Slovakia

Note: Paper in Slovak.

31 August 2013

Marmorkrebs found in Sweden, again

Apologies for being a bit behind the curve on this one, but I just saw the latest press release from back in July from the Swedish Agency for Marine and Water Management saying that Marmorkrebs had been found again this last summer, and in a different location that last autumn, and multiple individuals of different sizes.

This is not good news for Sweden, as it suggests Marmorkrebs are gaining a beachhead in that country.


Long overdue update, 30 June 2022: It wasn’t Marmorkrebs at all. It was still invasive, but a signal crayfish. It may have been a “mottled” colour pattern described here. The map is being updated.

External links

Nya fynd av misstänkt marmorkräfta har hittats i Västsverige

New Discoveries of Marbled Crayfish Cause Concern in Northern Europe (Note: English language press releases from this site do not appear to be archived as well as the Swedish language ones are.)

Picture from Swedish Agency for Marine and Water Management.

21 August 2013

Quoth the crayfish, "Nevermore"

There are about eight native crayfish species in Russia, and those crayfish have made an impression on the vernacular. This expression means, "Never":

когда рак на горе свистнет (kogdá rak na goré svístnet) — “When the crawfish whistles on the mountain”.

For more ways of saying "Never," see here. It misses a favourite of mine, though. Apparently, in ancient Rome, an expression for "never" was, "When a mule foals."

External link

When Pigs Fly, Crayfish Whistle, and It Snows Red Snowflakes

06 August 2013

Parthenogenesis primer

The Raptor Lab has a nice primer on parthenogenesis, although it focuses only on the phenomenon in pit vipers.

As if we required further proof life is weird, in walks parthenogenesis, an evolutionarily fascinating and frightening reproductive strategy, serving another round.

23 July 2013

What I’d like the next Syfy movie to be

Yes, in the wake of the viral success of Sharknado, I cannot help but pitch the next Syfy movie...

Volcanic base by Kröyer on Flickr; used under a Creative Commons license.

16 July 2013

“Five clawed” crayfish

Check this claw!

A fisherman collected this crayfish in Schoharie Creek, near Delanson, New York and took this quick picture before using this as bait. Here’s his reaction, recorded with his phone:

Being a neuro guy, I wondered if the extra segments have muscle and neurons, or whether they were just “blank” exoskeleton. The word I received was that the extra claw was not moving.

The picture and video made its way to a colleague, Frank Dirrigl, and eventually to me. I have never seen a deformity like on this crayfish before. Anyone ever seen anything like this before? Leave word in the comments!

Additional, 18 July 2013: This deformity is unusual, but not rare. You can get these sorts of outgrowths fairly easily following injury. In particular, Nakatani and colleagues (1998) show pictures that are very reminiscent of the one above. Thanks to Joe Staton, Marina Araújo, and Gerhard Scholtz for these references:


Araújo M, dos Santos TC. 2012. New record of malformation in the true crab Ucides cordatus (Linnaeus, 1763) (Crustacea, Decapoda, Ucididae), at Brazilian coast. Revista Nordestina de Zoologia, Recife 6(1): 15-19.

Mantellatto FLM, O'Brien JJ, Alvare F. 2000. The first record of external abnormalities on abdomens of Callinectes ornatus (Portunidae) from Ubatuba Bay, Brazil. Nauplius 8(1): 9-97.

Nakatani, I., Oshida, Y., Kitahara, T. 1998. Induction of extra claws on the chelipeds of a crayfish, Procambarus clarkii. The Biological Bulletin 195: 52-59.

Przibram, H. 1921. Die Bruchdreifachbildung im Tierreich. Wilhelm Roux Archiv für Entwicklungsmechanik der Organismen 48: 205-444.

Shelton, P.M.J., Truby, P.R., Shelton, R.G.J. 1981. Naturally occurring abnormalities (Bruchdreifachbildungen) in the chelae of three species of Crustacea (Decapoda) and a possible explanation. Journal of Embryology and Experimental Morphology 63: 285-304.

Pinheiro MAA , de Toledo TR. 2010. Malformation in the crab Ucides cordatus (Linnaeus, 1763)(Crustacea, Brachyura, Ocypodidae), in São Vicente (SP), Brazil. Revista CEPSUL - Biodiversidade e Conservação Marinha 1(1): 61-65.

Crossposted at NeuroDojo.

11 July 2013

Celebrate diversity: Rare boys

Artemia have featured on this blog before, mostly as possible food for Marmorkrebs. But like Marmorkrebs, there are parthenogenetic Artemia that reproduce asexually.


Maccari and colleagues show that Artemia sometimes produce little baby boy Artemia. There’re at low numbers; about 1% of offspring. I am impressed by just how many Artemia they looked at to determine this:

415 666 diploid parthenogenetic Artemia specimens were sexed in this experiment(.)

But while rare overall, a few sites, mostly in the Middle East were “hotspots” of male offspring, strongly indicating that there are population differences in this ability to produce males. This, in turn suggests that there may be situations in which this ability has an evolutionary advantage. That advantage might be that these males are completely fertile, and can mate with the females of sexual species that live in the same habitats. Maccari and company discuss the possibility that there are some advantages to having gene flow between species through this mechanism.

Additional, 12 July 2013: Carl Zimmer covers this paper at The Loom.


Maccari M, Gómez A, Hontoria F, Amat F. 2013. Functional rare males in diploid parthenogenetic Artemia. Journal of Evolutionary Biology: in press. DOI:

External links

The mystery of the rare male sea monkey

Photo by you get the picture on Flickr; used under Creative Commons license.

24 June 2013

Gallardo and Aldridge, 2013

Gallardo B, Aldridge DC. 2013. The ‘dirty dozen’: socio-economic factors amplify the invasion potential of 12 high-risk aquatic invasive species in Great Britain and Ireland. Journal of Applied Ecology 50(3): 757–766. http://dx.doi.org/10.1111/1365-2664.12079


  1. Aquatic invasive species are a growing concern to environmental managers because of their diverse impacts on aquatic biodiversity and high eradication costs, necessitating effective management policies. In this study, we evaluate the ability of environmental and socio-economic factors to predict the risk of invasion in Great Britain and Ireland of 12 potential aquatic invaders covering all major aquatic groups. Despite their potential to inform risk assessments, this is the first time socio-economic factors related to propagule pressure have been specifically integrated in distribution modelling.
  2. Species distribution models (SDM, MaxEnt algorithm) were calibrated with a set of environmental factors (e.g. bioclimatic, geographical and geological) and integrated with socio-economic (e.g. human influence index, population density, closeness to ports) predictors.
  3. The inclusion of socio-economic factors in SDM did not affect accuracy scores (AUC already >0·90), but their effects were more pronounced in spatial predictions, resulting in up to a sixfold amplification of the area predicted suitable for each species. Despite the inclusion of potential surrogates of water chemistry (e.g. geology) and propagule pressure (e.g. population density), temperature-related variables were most important predictors of aquatic species' distributions.
  4. According to SDM, the environmental suitability for a suite of invaders belonging to different taxonomic groups and regions of origin is greatest in east and south-east England and decreases towards the north and west. Multiple invasions in this region are of special concern, as species are known to modify their habitat facilitating subsequent invasions, thereby potentially exacerbating their impacts.
  5. Major management regions to be prioritized in monitoring programmes include the Humber, Thames and Anglian River Basin Districts. Species of special concern include a mysid (Hemimysis anomala), a gammarid (Dikerogammarus villosus), a plant (Ludwigia grandiflora) and two crayfishes (Procambarus clarkii and P. fallax).
  6. Synthesis and Applications. The inclusion of socio-economic factors in species distribution models has the potential to improve predictions of areas under a highest risk of multiple invasions and to help disentangle the complex interplay between biological invasions and global environmental and socio-economic processes. Such understanding is pivotal to prioritize limited resources for the optimum prevention and control of biological invasions.

Keywords: Ameiurus melasCorbicula fluminalisDikerogammarus villosusDreissena r. bugensisHemimysis anomala • Ludwigia grandiflora • MaxEnt • Neogobius melanostomusProcambarus sp. • species distribution models

Notes: Marmorkrebs is referred to in this paper as “Procambarus fallax.” The references and context make it clear, however, that the asexual Marmorkrebs are being modelled in this paper, not the sexual form of the slough crayfish.

The Supplemental material (S1) describes the European range of “P. fallax” as Germany and Great Britain. To the best of my knowledge, Marmorkrebs have never been found in the wild in Great Britain.

11 June 2013

The crayfish / crawfish / crawdad war

Business Insider features this heat map of what people call crayfish in the United States. It’s all very confusing.

First, the question asks what people call “miniature lobsters”. I’m not sure that’s helpful. Do you have any idea how many kinds of crustaceans are called “lobsters”? There are clawed lobsters, spiny lobsters, slipper lobsters, squat lobsters...

Second, I’m particularly puzzled by people use “crawdad.” Not that they do, but that there are two disconnected blobs of green. I would have expected more continuity.

Maybe Americans should follow the lead of the Australians and call them all “yabbies.”

Hat tip to P.Z. Myers.

External links

22 Maps That Show How Americans Speak English Totally Differently From Each Other
It’s “crawdads”!

21 May 2013


Sometimes, a druid’s just got to catch some crayfish.

In this short story by Kevin Hearne, “A Test of Mettle,” druid initiate Granuaile MacTiernan is tasked with controlling invasive crayfish:

With Sonora’s guidance, sensed through the turquoise sphere at the base of my throat, I can feel the flow of water there, feel the gentle slowness under the rock, the place where a large crawdad has made its home. A crawdad from the Midwest that doesn’t belong on this side of the continental divide, an invasive species that’s been killing off the native fish by eating their eggs. Elementary school kids dumped them in here at the end of their crustacean unit, and their teachers, who should have known better, let them ravage an ecosystem in the process.

This story, and some others, is available for free from Kevin’s website. Thanks, Kevin, for bringing crayfish to art!

External links

Kevin Hearne: Short Stories
Kevin Hearne on Twitter

02 May 2013

The Ecdysiast feature

The newest issue of The Crustacean Society’s newsletter, The Ecdysiast, is now available for viewing here. There are several articles of interest for readers. One is coverage of the SICB crayfish symposium that occurred in January It includes a note of the untimely death of Francesca Gherardi.

Also of interest are articles by Fred Schram, the general editor for the Journal of Crustacean Biology. In particular, “To be open or not to be open: That is the question” (page 7) is a look at open access from the perspective of someone in the thick of trying to maintain a journal in the face of a changing market, which includes declining Society membership.

Is OA the wave of the future? – maybe. However, we might suggest that “efficient” application of the OA model will lead to the collapse of many journals, especially those produced by small scholarly societies.

(Plug: If you are interested in crustacean biology, you should join the Society!)

22 April 2013

“Your heart stops”: Marmorkrebs in Scotland

Scotsman.com reports on the seizure of Marmorkrebs in the Central Belt.

Dr Colin Bean, science and policy advisor on freshwater biology at Scottish Natural Heritage, formally identified the recovered species in the current case.
He said: “Your heart stops really because American signal are bad enough. The biggest difference between marbled crayfish and other crayfish species is that the others need a male and a female to reproduce, but marbled crayfish are parthenogenic [reproduce asexually] which means you only need one to establish a population.

Yet again, these were Marmorkrebs sold through the pet trade. Kudos to the Scots for taking the task of monitoring exotics seriously:

Anyone caught in possession of non-native crayfish in Scotland can be jailed for up to six months and fined £40,000.

Some species distribution models suggest Scotland could be suitable habitat for Marmorkrebs. At right is an excerpt from Figure 3D in Feria and Faulkes (2011). There are three other models in that figure, and the other three predict much less habitat. Given the number of Marmorkrebs found in Europe since that paper was prepared, though, this version is probably the better reflection of the possible suitable habitat than the others.

Lastly, I appreciate that the news article carries on the European tabloid tradition of referring to small crayfish with monster movie descriptions, calling Marmorkrebs:

A voracious alien predator

Well, most crayfish do catch and eat other animals... but predator? Not what you would usually use to describe an omnivore that eats snails and other small benthic invertebrates.

External link

Scots wildlife at risk from alien crayfish breeds


Feria TP, Faulkes Z. 2011. Forecasting the distribution of Marmorkrebs, a parthenogenetic crayfish with high invasive potential, in Madagascar, Europe, and North America. Aquatic Invasions 6(1): 55-67. http://dx.doi.org/10.3391/ai.2011.6.1.07

05 March 2013

A third parthenogenetic crayfish species?

Probably not. This passage in a new paper by Rogowski and colleagues about the virile crayfish (Orconectes virilis; right) is interesting, however:

An interesting observation in the laboratory was the production of eggs and juveniles by a female that was collected in July and kept in isolation. This would suggest that females can maintain viable sperm for an extended period, potentially over 1 year (Reynolds, 2002), or that they will produce viable eggs even if they are not fertilised. Other crayfish have been known to reproduce clonally, for example Orconectes limosus (Buřič et al., 2011) and the marbled crayfish Procambarus fallax (Scholtz et al., 2003). Whether this individual maintained sperm from a previous mating or whether it was parthenogenetic is unknown.

If I were to bet, I would bet on sperm storage, which so many arthropods can do. While the evidence for Orconectes limosus being a facultative parthenogen is quite solid, even that has yet to be replicated. Either way, there seems to be much more work necessary to distinguish these two scenarios.


Rogowski DL, Sitko S, Bonar SA. Optimising control of invasive crayfish using life-history information. Freshwater Biology. in press. http://dx.doi.org/10.1111/fwb.12126


20 February 2013

Faulkes, 2013

Faulkes Z. 2012. How much is that crayfish in the window? Online monitoring of Marmorkrebs, Procambarus fallax f. virginalis (Hagen, 1870) in the North American pet trade. Freshwater Crayfish 19(1): 39-44. http://dx.doi.org/10.5869/fc.2013.v19.039


Marmorkrebs were discovered by European pet owners in the 1990s. Because there is no known native population of Marmorkrebs, the distribution of these crayfish is purely the result of human activity. Marmorkrebs are now spread throughout the pet trade worldwide and are introduced species in several countries. Given that the pet trade has been the suspected or confirmed source of introduction of many introduced species, I monitored online social activity for information about the use and spread of Marmorkrebs in North America. This revealed several new jurisdictions where Marmorkrebs had not been previously reported. Several records were found in jurisdictions where the local laws prohibited the owners from having Marmorkrebs. Tracking such records could be useful in determining the risk of Marmorkrebs introductions from release by pet owners.

Keywords: marbled crayfish • pet trade

18 February 2013

Remembering Francesca Gherardi

Oh, no.

Sad news indeed on the CRUST-L email list:

Dear friends,

we sadly have to inform you that yesterday our dear friend and colleague Francesca Gherardi passed away.

It was only weeks ago that I met Dr. Gherardi for the first time at the Society for Integrative and Comparative Biology meeting, where she was a speaker at the special session on crayfish. She was having terrible problems with her throat. She could barely whisper, but this did not diminish her presentation, once she got her hands on the microphone.

I caught a few pictures of her from the session; here is one.

She was a fine scientist, and will be much missed.

12 February 2013

“Most curious creature, Captain...”

I have to thank Nicole Gugliucci. Over the weekend, I was participating a a Google Plus hangout with Nicole and a few other people, describing some of the research I’ve been doing on the pet trade in Marmorkrebs. I made a comment like, “If you have Marmorkrebs as a pet, you always end up with surplus, because you can’t stop them from reproducing.”

And Nicole said, “They’re like tribbles.”

I was stunned. Marmorkrebs are totally like tribbles! How could I not have realized this before?

Dr. McCoy: [on reasons for the tribbles' high reproduction rate] Well, the nearest thing I can figure out is that they're born pregnant. Which seems to be quite a time saver.

Indeed, the original episode, “The Trouble With Tribbles,” contains this bit of dialogue that could be applied to any number of invasive species:

Spock: Surely you must have realized what would happen if you removed the tribbles from their predator-filled environment into an environment where their natural multiplicative proclivities would have no restraining factors.
Cyrano Jones: [all in one breath] Well, of cour... What did you say?
Spock: [irritated but patient] By removing the tribbles from their natural habitat, you have, so to speak, removed the cork from the bottle and allowed the genie to escape.

I am so going to use this comparison in a talk

06 February 2013

Shen and colleagues, 2013

Shen H, Braband A, Scholtz G. 2013. Mitogenomic analysis of decapod crustacean phylogeny corroborates traditional views on their relationships. Molecular Phylogenetics and Evolution 66(3): 776-789.


Phylogenetic relationships within decapod crustaceans are highly controversial. Even recent analyses based on molecular datasets have shown largely contradictory results. Previous studies using mitochondrial genomes are promising but suffer from a poor and unbalanced taxon sampling. To fill these gaps we sequenced the (nearly) complete mitochondrial genomes of 13 decapod species: Stenopus hispidus, Polycheles typhlops, Panulirus versicolor, Scyllarides latus, Enoplometopus occidentalis, Homarus gammarus, Procambarus fallax f. virginalis, Upogebia major, Neaxius acanthus, Calocaris macandreae, Corallianassa coutierei, Cryptolithodes sitchensis, Neopetrolisthes maculatus, and add that of Dromia personata. Our new data allow for comprehensive analyses of decapod phylogeny using the mitochondrial genomes of 50 species covering all major taxa of the Decapoda. Five species of Stomatopoda and one species of Euphausiacea serve as outgroups. Most of our analyses using Maximum Likelihood (ML) and Bayesian inference (BI) of nucleotide and amino acid datasets revealed congruent topologies for higher level decapod relationships: (((((((Anomala, Brachyura), Thalassinida: Gebiidea), Thalassinida: Axiidea), (Astacidea, Polychelida), Achelata), Stenopodidea), Caridea), Dendrobranchiata). This result corroborates several traditional morphological views and adds new perspectives. In particular, the position of Polychelida is surprising. Nevertheless, some problems can be identified. In a minority of analyses the basal branching of Reptantia is not fully resolved, Thalassinida are monophyletic; Polychelida are the sister group to Achelata, and Stenopodidea are resolved as sister group to Caridea. Despite this and although some nodal supports are low in our phylogenetic trees, we think that the largely stable topology of the trees regardless of different types of analyses suggests that mitochondrial genomes show good potential to resolve the relationship within Decapoda.

Keywords: mitochondrial genomes • Reptantia • Thalassinidans • Aliscore

05 February 2013

Soedarini and colleagues, 2013

Soedarini B, Klaver L, Giesen D, Roessink I, Widianarko B, van Straalen NM, van Gestel CAM. 2013. Effect of copper exposure on histamine concentrations in the marbled crayfish (Procambarus fallax forma virginalis). Animal Biology 63(2): 139–147. http://dx.doi.org/10.1163/15707563-00002401


Crustaceans can store excess copper in the hepatopancreas, an organ playing a role in digestive activity as well as in neurosecretory control. Here, we studied the effect of copper exposure on the level of histamine, an indicator of food spoilage in edible crustaceans. Histamine is also a neuromodulator in the intestinal nervous system of crustaceans, and a human allergen. Marbled crayfish (Procambarus fallax forma virginalis) were exposed to average measured values of 0.031 mg Cu/l and 0.38 mg Cu/l, respectively, for 14 days and then transferred to copper-free water for another 14 days. Concentrations of copper and histamine in the hepatopancreas and muscle were evaluated at different time points. Histamine levels were significantly higher in hepatopancreas and muscle tissues at the highest exposure level, but only after transfer of the animals to copper-free water. The increased histamine concentration following copper exposure may be explained by a (delayed) stress response, and by up-regulated histidine synthesis induced by copper, followed by decarboxylation to histamine.

Keywords: copper • hepatopancreas • histamine • intestinal nervous system • neuromodulator

11 January 2013

Updated map of introductions

Just wanted to post that the map of Marmorkrebs introductions has just been given a big update. In particular, it now includes all the locations listed in Chucholl et al. (2012). The map is not identical to Table 1 in that paper, however. The table only includes locations where there were either pictures of crayfish or voucher specimens to confirm the identification; my map includes some without those.

I’ve also used different placemarkers to distinguish locations with populations (dot in the middle of the placemarker) and those where there are single specimens, or the status is unclear (no dot).


Chucholl C, Morawetz K, Groß H. 2012. The clones are coming – strong increase in Marmorkrebs [Procambarus fallax (Hagen, 1870) f. virginalis] records from Europe. Aquatic Invasions 7: 511-519.

10 January 2013

Vogt, 2013

Vogt G. 2013. Abbreviation of larval development and extension of brood care as key features of the evolution of freshwater Decapoda. Biological Reviews 88(1): 81-116. http://dx.doi.org/10.1111/j.1469-185X.2012.00241.x


The transition from marine to freshwater habitats is one of the major steps in the evolution of life. In the decapod crustaceans, four groups have colonized fresh water at different geological times since the Triassic, the freshwater shrimps, freshwater crayfish, freshwater crabs and freshwater anomurans. Some families have even colonized terrestrial habitats via the freshwater route or directly via the sea shore. Since none of these taxa has ever reinvaded its environment of origin the Decapoda appear particularly suitable to investigate life-history adaptations to fresh water. Evolutionary comparison of marine, freshwater and terrestrial decapods suggests that the reduction of egg number, abbreviation of larval development, extension of brood care and lecithotrophy of the first posthatching life stages are key adaptations to fresh water. Marine decapods usually have high numbers of small eggs and develop through a prolonged planktonic larval cycle, whereas the production of small numbers of large eggs, direct development and extended brood care until the juvenile stage is the rule in freshwater crayfish, primary freshwater crabs and aeglid anomurans. The amphidromous freshwater shrimp and freshwater crab species and all terrestrial decapods that invaded land via the sea shore have retained ocean-type planktonic development. Abbreviation of larval development and extension of brood care are interpreted as adaptations to the particularly strong variations of hydrodynamic parameters, physico-chemical factors and phytoplankton availability in freshwater habitats. These life-history changes increase fitness of the offspring and are obviously favoured by natural selection, explaining their multiple origins in fresh water. There is no evidence for their early evolution in the marine ancestors of the extant freshwater groups and a preadaptive role for the conquest of fresh water. The costs of the shift from relative r- to K-strategy in freshwater decapods are traded-off against fecundity, future reproduction and growth of females and perhaps against size of species but not against longevity of species. Direct development and extension of brood care is associated with the reduction of dispersal and gene flow among populations, which may explain the high degree of speciation and endemism in directly developing freshwater decapods. Direct development and extended brood care also favour the evolution of social systems, which in freshwater decapods range from simple subsocial organization to eusociality. Hermaphroditism and parthenogenesis, which have evolved in some terrestrial crayfish burrowers and invasive open water crayfish, respectively, may enable populations to adapt to restrictive or new environments by spatio-temporal alteration of their socio-ecological characteristics. Under conditions of rapid habitat loss, environmental pollution and global warming, the reduced dispersal ability of direct developers may turn into a severe disadvantage, posing a higher threat of extinction to freshwater crayfish, primary freshwater crabs, aeglids and landlocked freshwater shrimps as compared to amphidromous freshwater shrimps and secondary freshwater crabs.

Keywords: marine-freshwater transition • Crustacea • life-history • development • parental care • trade-off • speciation • social systems • extinction threat

08 January 2013

SICB 2013 special session on crayfish

The special session on crayfish biology at SICB may well have been one of the busiest days for Marmorkrebs news and announcements in a long while. There were at least three major pieces of new information about our favourite crustacean.


Peer Martin provided evidence that Marmorkrebs are triploid. This is an important step forward in understanding the original of asexual reproduction in this species. This strongly suggests that this may have been a "one off" chance event, either through some sort of incomplete separation of chromosomes or duplication of chromosomes, or hybridization.

Crayfish plague

As part of Peer Martin's talk, he discussed whether Marmorkrebs are "the perfect invader" as they were so memorably called. He included a discussion about the importance of crayfish plague as an issue in the invasive potential for Marmorkrebs. In the questions, I asked whether anyone had actually tested whether Marmorkrebs carry the plague, or whether it was simply assumed they were resistance, because essentially all North American species are. There is apparently one doctoral thesis that reports a Marmorkrebs carrying crayfish plague. That said, many in the lab, and one wild-caught animal, have tested for the disease.

More introductions in the wild

Chris Chucholl reported that there are now six confirmed populations in Europe, five of which are in Germany. During my talk, I reported the "breaking news bulletin" that I'd blogged while waiting in line at Starbuck's for a croissant that Marmorkrebs had been found in Sweden. Tadashi Kawai mentioned that a population had been found in Sapporo, but that it apparently died out.

Other highlights

Marmorkrebs was not the only only game in town in this session, however.

Tonio Garza de YTa discussed his experiences over a decade in working with farmers to develop sustainable, productive, profitable aquaculture for red-clawed crayfish in Mexico. The lessons he had were to develop the market first. There is no point in producing food nobody will buy. Secondly, make sure your product does not give itself away. The red-clawed crayfish got away from their cultured ponds and successfully established populations, which could be harvested more cheaply than the aquacultured crayfish.

Francesca Gherhardi talked about the importance of understanding behaviour of potentially invasive species. To give just one example, she examined the interaction between temperature and fighting between different invasive crayfish species. Spinycheek crayfish (Orconectes limosus) become more less active and more likely to seek shelter as temperatures increase. Signal crayfish (Pacifastacus leniusculus) become less competitive as water warms. Red swamp crayfish (Procambarus clarkii) change their aggressive behaviour very little, meaning swamp crayfish are poised to be the winners as temperatures warm under climate change.

Incidentally, my sympathy goes to Francesca, who was having quite severe voice problems. She had to whisper her whole talk. This worked to her advantage, as it gave her presentation an urgent, conspiratorial tone

Keith Crandall talked somewhat about some new research he is co-authoring on crayfish relationships, but much of his talk was geared to discussing tree of life projects. In particular, I’m excited about opentreeoflife.org. Most taxonomic papers now are published as PDFs, which are great to look at, but hard to re-use any data in them.

The goals of the Open Tree of Life project are, in part, things near and dear to much of the online science community. They want to encourage refinement of the tree, annotation, and promote a culture of data sharing, not simply publication. Currently, people are as consistent about putting things into Treebase or Dryad as they are into GenBank.

Oh yes, and they want to assemble a complete tree of life in three years. Keith mentioned that the National Science Foundation has been supporting various tree of life related projects for about a decade now, and are getting quite eager to see a tree. This project will make it easier to identify holes in the existing tree.

A great session marred only by the fact that I had to run to catch my plane, and couldn’t stay and chat more with  the other speakers! Much thanks to Tadashi Kawai for organizing the session!

07 January 2013

First record of Marmorkrebs in Sweden

I am preparing for today's crayfish special session at SICB, but this is too imporatant not to share immediately: marbled crayfish found in the wild in Sweden.

I will try to discover more details soon.

Update, 8 January 2013:

I have found the original press release from 5 December 2012. It describes the find of Marmorkrebs in the river “a few weeks ago,” so about November. That there are “several sizes” is suggestive of a population, but does not confirm it.

The map of Marmorkrebs introductions has been updated accordingly.

01 January 2013

2012 was an average year for Marmorkrebs research

After the boom of 2010 and the bust of 2011, Marmorkrebs research publications are back on a more even keel this year...

That’s not including Chucholl, 2013, which, despite an official 2013 publication date, was published in December.

2013 shall start with a bang, with the crayfish symposium at the Society for Integrative and Comparative Biology in San Francisco in mere days!